Stents are an established method of treatment for conditions such as stenosis, occlusions, and other lesions within a patient's vascular system or other body lumens. An unexpanded stent is typically delivered on a catheter and expanded in place to dilate the treatment site and provide support to the lumen walls. The stent may be self-expanding, in which the stent is biased to expand when a constraint, such as when a sheath is removed. Other stents may require the use of a balloon within the stent to expand the stent.
Lesions and other conditions may occur at any location within a body lumen. In a location where a branch vessel extends from a main vessel, termed an “ostium,” the branch vessel typically has a tapered section extending from the main vessel into the branch vessel. When a lesion occurs within the ostium, placement of a stent can become difficult because of the tapered section.
FIG. 1 illustrates a standard balloon catheter 100 inflated within an ostium 102 of a body lumen. The standard balloon catheter 100 is shown with a balloon 103 in an inflated state within the body lumen. The inflated state would typically be used to dilate the lumen and/or expand a stent (not illustrated). The body lumen has a tapered portion 104 in which a side branch 106 enters a main lumen 108. The balloon 103 interacts with the tapered portion 104 of the side branch 106 causing a force in a proximal direction 112 of the side branch 106. As a result, the balloon 103 may shift in the distal direction when fully inflated. This effect is dependent upon the magnitude of the taper and the length of the balloon 103 relative to the tapered portion 104. This may result in the stent being positioned in a location different from what was originally intended. It would be beneficial to deliver and expand a stent within an ostium while avoiding the “watermelon seed effect” to ensure the proper placement of the stent.